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The analysis of failure behaviors of continuous fiber-reinforced ceramic matrix composites (CMCs) requires the characterization of the damage evolution process. In service environments, CMCs exhibit complex damage mechanisms and failure modes, which are affected by constituent materials, meso architecture, inherent defects, and loading conditions. In this paper, the in-plane tensile mechanical behavior of a plain woven SiCf/SiC CMC was investigated, and damage evolution and failure process were studied in detail by digital image correlation (DIC) and acoustic emission (AE) methods. The results show that: the initiation of macro-matrix cracks have obvious local characteristic, and the propagation paths are periodically distributed on the material surface; different damage modes (matrix cracking and fiber fracture) would affect the AE energy signal and can be observed in real-time; the significant increase of AE accumulated energy indicates that serious damage occurs inside the material, and the macroscopic mechanical behavior exhibits nonlinear characteristic, which corresponds to the proportional limit stress (PLS) of the material.

Recently, carbon fiber-reinforced silicon carbide (C/SiC) composites are considered important candidates for laser protection materials. In this paper, the ablation mechanism of C/SiC composites and their modified composites under laser irradiation was studied. ZrB2–MoSi2–SiC ternary-phase ceramic was successfully coated on C/SiC composites by using high velocity oxygen fuel (HVOF) technology, with Mo as transition layer. The evolution of phase and morphology of the composites was investigated by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ablation behavior of composites was investigated by laser confocal microscopy (LCM). The results showed that the ablation mechanism of composites was controlled by phase transformation, thermal reaction and thermal diffusion. The solid-liquid transition of ZrB2 and MoSi2 was the dominant factor. Thermal reaction and good thermal diffusivity of coatings were also important factors affecting the ablation performance. ZrB2–SiC– MoSi2/Mo coating failed when all phase transitions were completed and no continuous liquid phase was formed, followed by rapid damage of C/SiC substrate. The results of this work can provide theoretical guidance and research ideas for the design and application of laser protective materials.

In this paper, the SiC/SiC high-pressure turbine twin guide vanes were fabricated using the chemical vapor infiltration (CVI) method. Cyclic thermal shock tests at different target temperatures (i.e., 1400, 1450, and 1480 °C) in a gas environment were conducted to investigate the damage mechanisms and failure modes. During the thermal shock test, large spalling areas appeared on the leading edge and back region. After 400 thermal shock cycles, the spalling area of the coating at the basin and back region of the guide vane was more than 30%, and the whole guide vane turned gray, due to the formation of SiO2. When the thermal shock temperature increased from 1400 to 1450 and 1480 °C, the spalling area of the basin and the back region of the guide vane did not increase significantly, but the delamination occurred at the tenon, upper surface of the guide vane near the trailing edge of the guide vane. Through the X-ray Computed Tomography (XCT) analysis for the guide vanes before and after thermal shock, there was no obvious damage inside of guide vanes. The oxidation of SiC coating and the formation of SiO2 protects the internal fibers from oxidation and damage. Further investigation on the effect of thermal shock on the mechanical properties of SiC/SiC composites should be conducted in the future.

A Ni(TFA)2-catalyzed ortho-trifluoromethylation of 8-aminoquinoline derivatives was developed by acyl-directed C–H functionalization. A series of 7-trifluoromethylquinolinamine derivatives were originally obtained with moderate to excellent yields by using TMSCF3 as the trifluoromethylation reagent under mild conditions. In addition, the reaction mechanism is proposed and proved by the related experiment.

We demonstrated an optical fiber sensor based on a cascaded fiber Fabry-Perot interferometer (FPI)-regenerated fiber Bragg grating (RFBG) for simultaneous measurement of temperature and strain under high temperature environments. The FPI is manufactured from a ∼74 µm long hollow core silica tube (HCST) sandwiched between two single mode fibers (SMFs). The RFBG is inscribed in one of the SMF arms which is embedded inside an alundum tube, making it insensitive to the applied strain on the entire fiber sensor, just in case the temperature and strain recovery process are described using the strain-free RFBG instead of a characteristic due-parameter matrix. This feature is intended for thermal compensation for the FPI structure that is sensitive to both temperature and strain. In the characterization tests, the proposed device has exhibited a temperature sensitivity ∼ 18.01 pm/°C in the range of 100 °C - 1000 °C and excellent linear response to strain in the range of 300 °C - 1000 °C. The measured strain sensitivity is as high as ∼ 2.17 pm/µɛ for a detection range from 0 µɛ to 450 µɛ at 800 °C, which is ∼ 1.5 times that of a FPI-RFBG without the alundum tube.

A visible-light-induced decarboxylation coupling/intramolecular cyclization is reported. The one-pot synthesis system provides mild, efficient, and atom economical access to the synthesis of 4-aryl-2-quinolinone derivatives. It is notable that the necessary oxidant in the traditional decarboxylation coupling is replaced by the visible-light irradiation in this paper. In addition, the HBV inhibitor is synthesized by the one-pot synthesis system in an atom economical manner.

A T300 carbon fiber and a SiC-coated C/SiC composite made from the same fiber were studied in atomic oxygen environment. The carbon fiber shows significant degradation while the erosion rate of SiC-coating of C/SiC is about 50 times lower. Evidence shows that Si is preferentially etched from the SiC surface. And XPS information showed that amorphous carbon and diamond-like carbonare periodically generated on the tested composite surface. Statistical analysis shows that the C/SiC specimens have no significant change in flexural properties after 1-year fluence AO treatment.

Ceramic matrix composite (CMC) integrated with various advanced properties is a promising material in many space projects. In those applications, CMC will be subjected to various extreme environments with temperature range of −170 to 2000 ◦ C as well as space particles. A series of methods have been developed to simulate different stage of severe environment, i.e., launching stage, staying stage and re-entry stage. C/SiC related materials have been investigated by these simulation methods. A lot of useful information obtained by the series of simulation methods have been remarkably enhanced our understanding on the behavior of CMC used for RLV hot structures.

We have experimentally demonstrated an optical fiber Mach-Zehnder interferometer (MZI) structure formed by a few-mode photonic crystal fiber (PCF) for curvature measurement and inscribed a fiber Bragg grating (FBG) in the PCF for the purpose of simultaneously measuring temperature. The structure consists of a PCF sandwiched between two multi-mode fibers (MMFs). Bending experimental results show that the proposed sensor has a sensitivity of −1.03 nm/m−1 at a curvature range from 10 m−1 to 22.4 m−1, and the curvature sensitivity of the embedded FBG was −0.003 nm/m−1. Temperature response experimental results showed that the MZI’s wavelength, λa, has a sensitivity of 60.3 pm/°C, and the FBG’s Bragg wavelength, λb, has sensitivity of 9.2 pm/°C in the temperature range of 8 to 100 °C. As such, it can be used for simultaneous measurement of curvature and temperature over ranges of 10 m−1 to 22.4 m−1 and 8 °C to 100 °C, respectively. The results show that the embedded FBG can be a good indicator to compensate the varying ambient temperature during a curvature measurement.